Production of nitrogen-phosphorus compounds

ABSTRACT

A vapor phase reaction process for production of concentrated nitrogen-phosphorus compositions. The process involves simultaneous reaction of elemental phosphorus with a low proportion of input ammonia and an excess of oxygen (air) in a single-stage reactor. Reactor is maintained at about 500* to 1300*F. Retention time of gases in reactor ranges from about 0.5 to 3.5 seconds at operating conditions. Product of the reaction gases is collected as dry, white, amorphous solid. Products contain 14 to 16 percent N, 31 to 33 percent P, and up to 91 percent total plant nutrient content (N + P2O5 equivalent). Water solubility of the solid products is in the range from about 90 to 100 percent. Greenhouse tests indicate that the products are fully effective as fertilizer.

United States Patent Lewis, Jr. et a1.

14 1 Nov. 25, 1975 PRODUCTION OF NITROGEN-PHOSPHORUS COMPOUNDSInventors: Harry T. Lewis, Jr.; John G.

Getsinger, both of Florence, Ala.

Assignee: Tennessee Valley Authority, Muscle Shoals, Ala.

Filed: Oct. 9, 1973 Appl. No.: 404,233

Christian 71/35 Lewis.... 71/34 Primary E.\'aminer-J0hn Adee Attorney,Agent, or Firm-Robert A. Petrusek [57] ABSTRACT A vapor phase reactionprocess for production of concentrated nitrogen-phosphorus compositions.The process involves simultaneous reaction of elemental phosphorus witha low proportion of input ammonia and an excess of oxygen (air) in asingle-stage reactor. Re-

actor is maintained at about 500 to 1300F. Reten- 1521 us. 01. 71/34;71/49 tion time of gases in reactor ranges from about 05 to 1511 1111.C1. COSB 7/00 Seconds at operating conditions- Product of the [58] Fieldof Search 71/34, 32, 49; 423/305, action gases is collected as dry,White amorphous 423/307 315 314 solid. Products contain 14 to 16 percentN, 31 to 33 percent P, and up to 91 percent total plant nutrient [56]References Cited content (N P 0 equivalent). Water solubility of theUNITED STATES PATENTS solid products is in the range from about 90 to100 percent. Greenhouse tests indicate that the products 825k?" 71/32 Xare fully effectiveas fertilizer. r1s1an..... 2,839,376 6/1958 Christian71/32 9 Claims, 3 Drawing Figures AMMONIA f 3. N2, 02 (RECYCLE) AMMONIARECOVERY UNIT PHOSPHORUS I AMMONIA OR 12 BYPRODUCT he REACTOR 3 AIR M fF DRYER COOLER COLLECT-OR REACTION PRODUCT AIR FLOW SHEET FOR REACTINGAMMONIA, PHOSPHORUS AND OXYGEN (AIR) US. Patent Nov. 25, 1975 Sheet 2 of3 3,922,157

' P4 SATURATOR EXIT GASES TO AMMONIA RECOVERY UNIT {ELECTROSTATICPRECIPITATOR PHOSPHORUS REACTION (PYREX) THERMO- COUPLES REACTOR(MULLITE TUBE) PRODUCT Fig. 2

APPARATUS FOR SINGLE-STAGE REACTION OF PHOSPHORUS, AMMONIA, AND OXYGENUS. Patent Nov. 25, 1975 Sheet30f3 3,922,157

O O O O n v 8 6 4 M9528 o x. 526% 9.4 6202 w E REACTOR DIAMETER, IN. L02.0 3.0 4.0 5.0 6.0

SURFACE AREA: VOLUME RATIO 4.00 2.00 L33 L0 0.8 0.67

Fig. 3

. EFFECT OF REACTOR SURFACE AREA:

VOLUME RATIO ON RECOVERY OF,

NONGLASS PRODUCT FROM NH P O REACTION PRODUCTION OF NITROGEN-PHOSPHORUSCOMPOUNDS The invention herein described may be manufactured and used byor for the Government for governmental purposes without the payment tous of any royalty therefor.

This application is a continuation of our copending application Ser. No.341,908, filed Mar. 16, 1973, for PRODUCTION OF NITROGEN-PHOSPI-IORUSCOMPOUNDS.

Our invention relates to an improvement in method for production ofnitrogen-phosphorus compositions; more particularly it relates to theproduction of a new composition of matter by simultaneously reactingvapors of ammonia, phosphorus, and oxygen (air) in a single-stagereactor to yield dry, free flowing solid products of extremely highwater solubility, about 90 percent at 77F and even up to 100 percentwater solubility at 77F of the nitrogen and P contents of the material.The solid products are highly concentrated in phosphorus (up to 33.2percent) and in total plant nutrient (N P 0 equivalent) up to 91 percentor up to -76-0 (NP O K O) grade. These products are finished fertilizermaterials, not intermediate products requiring hydrolysis to yieldmaterials suitable as fertilizers.

Heretofore the action of ammonia on phosphorus pentoxide has beenstudied by a number of investigators beginning, we believe, with thework of Schiff (Liebigs Ann. 103, 168-1857). Sanfourche et al. (BullSoc. Chim. 47, No.4, 273-9 1930), in a paper describing their ownstudies, reviewed the work of previous investigators. In the small-scalework by Sanfourche et al., red phosphorus was burned with a mixture ofair and nitrogen, ammonia was added to the combustion products, and thereaction product was collected in jars. These workers investigated theeffect of the amount of moisture in the combustion air and found thatthey obtained low yields of product when they used artificially driedair. They postulated their reaction to be P 0 BNH, H,0 P,O;,NH,(0N1-l)=OI-l (Diammonium amidopyrophosphate) Methods for preparing ammoniummetaphosphate from phosphorus, air, water, and ammonia also have beenproposed. Among the methods proposed are those described by Ross et al.(U.S. Pat. No. 1,194,077) and by Rice (U.S. Pat. Nos. 2,561,415 and2,689,780), and by Arvan (U.S. Pat. No. 2,958,577). In Rice U.S. Pat.No. 2,561 ,415, for example, the reaction temperature is between 600 and900F and his proddct contains 32 percent P, whereas in Arvan U.S. Pat.No. 2,958,577 the reaction temperature is in the range from 390 to 1110Fand Arvans products, one of which is reported to be a metaphosphate,contains above about 30 percent P.

According to these methods, phosphorus is burned with air containingmoisture, and the resulting phosphorus pentoxide is reacted withammonia. The product of this reaction is collected as a white, fluffypowder. The following reaction is presumed to take place:

P 0, H ZNH 2NH,P0, If the air used to burn the phosphorus containsinsufficient water to satisfy the requirement for the reaction,additional water is added to the system.

Woodstock, in U.S. Pat. No. 2,122,122, describes a process in whichammonia is reacted with solid phosphorus pentoxide.

Somewhat more recently, reactions involving ammonia, phosphorus, andoxygen, namely NH P O reactions, have been studied by a number ofinvestigators. Driskell (U.S. Pat. No. 2,713,536) burned phosphorus indry air and ammoniated the hot combustion gases at about 600F. A typicalproduct contained 33.9 percent P, had limited solubility in water, andwas highly hygroscopic. Hignett et al (U.S. Pat. No. 2,856,279) firstproduced a product similar to Driskells and then hydrolyzed andagglomerated the material in a rotary tumbler at about 250F with steamto reduce its hygroscopicity and increase its bulk density. Jones (U.S.Pat. No. 3,131,992) obtained materials of low water solubility (10-30percent by weight) by burning phosphorus with dry air, cooling thecombustion products (preferably in the range from 450 to about 950F),and then adding anhydrous ammonia. In still another patent (I-Iibbettset al., U.S. Pat. No. 3,226,222) phosphorus pentoxide is suspended in aliquid hydrocarbon such as N-heptane, ammonia added in a pressure vesselat 50 psi and the temperature maintained in the range from about 120 toabout 300F, with the reaction product separated by filtration. By thislatter method, hygroscopic products of about 27-67-0 grade (29.3 percentP) were obtained.

Christian (U.S. Pat. No. 2,839,376) and Lewis, Jr. (U.S. Pat. No.3,539,328), unlike the prior art referred to supra, eliminated thephosphorus oxidation step prior to ammoniating the combustion gases. Theworks of these inventors involved a simultaneous reaction of vapor phasemixtures of ammonia and oxygen'with phosphorus. The reaction was carriedout in a twostage reactor.

In Christians process, phosphorus vapors are reacted with oxygen,ammonia, and nitrogen at temperatures below about 300F, followed bypassage of the reaction gases through a second reaction zone maintainedabove 570F and below 1110F and preferably in the range from about 800 toabout 1100F. In this process of Christian, the product collected in theelastrostatic precipitator is described as a white, dry powderessentially nonhygroscopic and with limited solubility in water. Atypical ultimate analysis thereof is a grade 2173-0 (31.9 percent P).

In essence, the novelty of the invention of Lewis U.S. Pat. No.3,539,328 consists of l a simultaneous reaction of ammonia, phosphorus,and oxygen at temperatures higher than those used and taught byChristian with an unexpected result in solid products therefrom of bothhigher phosphorus and total plant nutrient (N P 0 equivalent) contentsand (2) a method of hydrolyzing the products to yield materialseminently suitable as fertilizers. Lewis maintains the temperature inthe first stage of the reactor between 950 to 1065F. On the other hand,Christian carries out his first-stage of the reaction at much lowertemperatures, i.e., at about 300F and preferably between about 195 to285F. In the second-stage reactor of Lewis process the reactiontemperature is maintained above about 1200F, preferably between 1400 andabout 1600F, and still most preferably between about 1400 and 1500F. Onthe other hand, Christian teaches passing the reaction gases through asecond-stage reaction zone maintained at much lower temperatures, i.e.,above 570F and in his preferred embodiment between about 800 and 1 F.

The solid reaction products obtained by the process of Lewis containconsiderably more phosphorus than those reported by Christian, i.e.,about 34 percent to about 41 percent as compared with 30 percent toabout 32 percent. Lewis products contain 12 to 20 percent nitrogen. Thewater solubility of the solid products obtained by Lewis in histwo-stage process is predetermined and is in the range from about 20 to95 percent. The product may be further solubilized by hydrolyzing itwith aqueous medium (water, water vapor, steam, and mixtures thereof) at212 to 400F and 240 psig for about 5 to 60 minutes.

The molecular structure of the products obtained by Lewis in histwo-stage process is not known. Petrographic, electron microscope, andX-ray analysis indicate that some of the products are amorphous gels andothers are mixtures of gels together with minor phases of monoammoniumorthophosphate and unidentifiable crystal phases. Chromatographicanalyses indicate that the phosphorus in his products is present in ahighly condensed form; the soluble phosphates (0.5 N NaOH) aredistributed as 7 to 40 percent orthophosphate, 25 to 60 percentpyrophosphate to nonapolyphosphates, and to 55 percent as polyphosphatescontaining more than 9 phosphorus atoms in the molecule. Infraredanalysis suggests that the products are polyphosphate polymerscontaining some PN and PNO linkages as well as P-OP linkages.

Christian, in another patent (U.S. Pat. No. 2,884,318), teacheseliminating the phosphorus oxidation step prior to ammoniating thecombustion gases. In

that sense, his work, like that of the present invention, involves'asimultaneous reaction of vapor phase mixtures of ammonia and oxygen withphosphorus in a single-stage reactor. In Christians process elemental Pis contacted with gas mixtures of oxygen, ammonia, and nitrogen atreaction temperatures below about 300F. The product is cooled andcollected in a bag filter or electrostatic precipitator. He teaches thathis product is substantially nonhygroscopic and substantially insolublein water, and a typical ultimate analysis thereof is a grade of l9690(30.l percent P). In neither of the two patents of Christian is there adisclosure of tests or the like to show. the effectiveness of hismaterials as fertilizers. He teaches only that the material may beapplied conventionally to plants in the form of an aqueous dispersion orsuspension.

Our invention is directed to an improved method for producingnitrogen-phosphorus compositions. In essence, the novelty of ourinvention consists of a simultaneous exothermic reaction of elementalphosphorus with a low proportion of ammonia and an excess of oxygen in asingle-stage reactor at temperatures between about 500 to 1300F to yieldhighly concentrated water-soluble materials eminently suitable asfertilizers.

The molecular structure of our new solid products is not now known.Petrographic analysis indicates that the products are amorphousmaterials that contain traces of crystalline species; the refractiveindex of the products is in the range of long-chain ammoniumpolyphosphates. The infrared spectra suggest that the water-solubleportion of the products are long-chain ammonium polyphosphates and thatthe small proportions of water-insoluble material are similar to (PNO),type compounds. Chromatographic analyses of the products indicate thatmost of the soluble phosphates (0.5 N NaOH) are polyphosphates. Thesoluble phosphates are distributed as 3 to 6 percent orthophosphate, 2to 6 percent pyrophosphate, l to 4 percent as tripolyphosphate, and 84to 94 percent as polyphos- 4 phates containing more than threephosphorus atoms in the molecule.

Our new single-stage process for producing nitrogen and phosphoruscompositions is a significant improvement over both the teachings ofLewis and the teach ings of Christian supra whereby the simultaneousreaction of ammonia, phosphorus, and oxygen is carried out in atwo-stage process. Our single-stage process simplifies reactorconstruction and operation, thus reducing cost in a process scale-up.Since our single-stage process requires only one instead of two heatingzones, the need for heating between stages is eliminated and fewercontrol devices and less equipment are required.

Our new single-stage process wherefrom is eliminated the separatephosphorus-oxidation step prior to ammoniation is a substantialimprovement on the teachings of the single-stage process of Christian asfollows:

l In our process, the temperature of the single-stage reactor ismaintained at greater than 400F and less than l350F, preferably betweenabout 500 and about l300F and still more preferably at 600 to l 150F. Onthe other hand, Christian teaches passing the reaction gases through thereaction zone at much lower temperatures, i.e., below about 300 andpreferably between 77 and about 250F. Our process would require lesscooling capacity than Christians process.

2. In our process, we control and proportion the introduction of saidvapors of ammonia, oxygen, and elemental phosphorus into the reactionzone (single-stage reactor) to maintain therein (a) an excess of oxygenin the range greater than 120 percent and up to about 800 percent limit(for reasons of economy) and preferably about 375 percent to about 600percent (all percents by weight) of that required to yield an 0 2R, moleratio of 5, and (b) a quantity of ammonia greater than about 50 percentand less than about 80 percent and preferably in the range from about 60to about 70 percent of that required to yield an N:P atomic ratio of 2.The reaction mixture of vapors of ammonia, oxygen, and phosphorus in ourprocess consists of between about 6 percent and about 19 percent byvolume of oxygen (equivalent to between about 29 percent and aboutpercent by volume of dry air), between about 0.9 percent and about 4.8percent by volume of anhydrous ammonia, between about 0.2 and about Ipercent by volume of phosphorus, and the remainder as a nonreactive orinert gas at reaction temperature, such as nitrogen. On the other hand,Christian teachesintroducing phosphorus into the reaction zone in gasmixtures that contain less oxygen (0.1 to 5 volume percent vs. about 6to about 19 volume percent) and more anhydrous ammonia (5 to 50 volumepercent vs. about 0.9 to about 4.8 volume percent); the remainder of thegas mixture is nonreactive at reaction temperature. Since the ammoniaconcentration is lower in our process, the requirements for recovery ofexcess ammonia would be less. The solid reaction products obtained byour single-stage process contain more phosphorus than those reported byChristian, i.e., about 31 to 33 percent as compared with about 30percent.

3. In our process, new solid products of extremely high water solubility(about 90 to I00 percent of both N and P values at 77F) have beenobtained. Greenhouse tests, to be discussed later, show that our highlywater-soluble solid products are eminently suitable as fertilizers.Christian teaches that his solid product is substantially insoluble inwater and has low or limited 5 solubility. He teaches only that thematerial is stable enough to be applied to plants in the form of anaqueous dispersion or suspension. Tests of the use of his product as afertilizer appear to be unreported.

4. The solid products produced by our process are white, dry materialswith good storage properties. They contain from about 14 to 16 percentnitrogen and 31-33 percent phosphorus (71 to 76 percent P equivalent)and are highly concentrated in total plant nutrients (N P 0 equivalentup to 91 percent). In addition, the N:P O weight ratios in the productsfrom practicing our invention ranged from about 0.19 to 0.23. On theother hand, Christian teaches that the solid product from his inventioncontained about 19 percent by weight of nitrogen and about 30 percent byweight of phosphorus and corresponds to about 19-6- 9-0 grade and an N:PO weight ratio of 0.28, which is not in the range of the new solidproducts obtained in our invention. In Christians teaching, there is nodisclosure of retention time of the reaction gases in the reaction zone.In our new process, the residence of vapors of ammonia, oxygen (air) andelemental phosphorus is maintained in the single-stage reaction zone inthe range of less than 4 seconds and greater than 0.1 second, preferablyfrom about 0.5 to about 3.5 seconds, and still more preferably for about1 second.

It is therefore an object of the present invention to produce a newcomposition of matter by the simultaneous vapor phase reaction ofammonia, phosphorus, and oxygen (air) in a single-stage reactor yieldwhite, dry, free-flowing solid products which are highly water soluble(about 90 percent of both N and P at 77F and up to 100 percent watersolubility of the N and P at 77F) wherein the phosphorus-oxidation stepprior to ammoniation of the combustion gases is completely eliminated.

Another object of our present invention is to produce a new compositionof matter by simultaneously reacting vapors of ammonia, phosphorus, andoxygen (air) in a single-stage reactor, that is eminently suitable asfertilizer material for direct application to the soil wherein thephosphorus-oxidation step prior to ammoniation of the combustion gasesis completely eliminated.

Another object of the present invention is to produce a new compositionof matter by the vapor-phase reaction of ammonia, phosphorus, and oxygen(air) in a single-stage reactor to yield dry, free flowing solidproducts which are highly concentrated in phosphorus (up to 33.2percent) and in total plant nutrients (N P 0 equivalent up to 91percent) wherein the phosphorusoxidation step prior to ammoniation ofthe combustion gases is completely eliminated.

A further object of the present invention is to yield our desiredresults described above wherein the phosphorus-oxidation step prior toammoniation is completely eliminated and wherein is incorporated thesimultaneous reaction of ammonia, phosphorus, and oxygen in asingle-stage reactor at substantially higher temperatures and withhigher proportions of O :P and lower proportions of NI-I :P in thereaction gas mixtures than taught by the prior art for a single-stageprocess.

Still further and more general objects and advantages of the presentinvention will appear from the more detailed description set forthbelow, it being understood, however, that this more detailed descriptionis given by way of illustration and explanation only and not by way 6 oflimitation since various changes therein may be made by those skilled inthe art without departing from the spirit and scope of the presentinvention.

Our invention, together with further objects and advantages thereof,will be better understood from a consideration of the followingdescription taken in connection with the accompanying drawings in which:

FIG. 1 is a flowsheet illustrating the principles utilized in carryingout our invention.

FIG. 2 is a diagram of the equipment we used on small-scale tests of ourprocess for producing the solid products comprising our new compositionof matter.

FIG. 3 is a curve showing recovery of phosphorus as nonglass product(dry, white solid materials) versus reactor surface area volume ratiofor tests in the various diameter single-stage reactors.

Referring now more specifically to FIG. 1, air is passed through-airdryer 1 to reduce the moisture content thereof that the presence ofwater vapor reduces the grade of-the P.,NH *O reaction products. Thedried air together with ammonia and phosphorus, all being in the..-.vapor phase, are introduced into reactor tube 2. The reaction isexothermic and requires little or no external heat. Depending on theproduction rate,

cooling of reactor 2, although not shown, may be necessary. Upon leavingreactor 2, the gases pass through cooler 3 and into collector 4 wherethey are removed in the form of dry, white powders. Effluent leavingcollector 4 passes to point 5 where-the effluent is split. The majorpart of the effluent is recycled to point 6. The remaining portion ofthe effluent is bled off to maintain a constant N :P ratio in the feed.This portion of the effluent passes to ammonia recovery unit 7. Inammonia recovery unit 7, the ammonia may-be recovered in an acid orwater scrubber or by any other suitable means.

Referring now more specifically to FIG. 2, there is shown a diagram ofthe equipment we used on tests of the scale smaller than that of acommercial plant and of a size generally referred to as bench-scale. Asmay be seen, the phosphorus vapor was fed by means of a saturator to thereactor maintained at a temperature in the range of 400 to I350F.Simultaneously, ammonia, oxygen as dried air, and nitrogen, if desired,were metered to the reactor. The gases leaving the reactor were cooledand collected in an electrostatic precipitator as dry, white powders.Effluent from the precipitator passed through the ammonia recovery unit.The retention time of gases in the reactor, maintained in thetemperature range of 400 to 1350F, ranged from 0.1 to 3.5 seconds. Thedesired retention time was maintained by varying either the volume ofthe feed gases or the proportion of the reactor tube that was heated attest temperature. The oxygen (dried air) input ranged from 120 percentup to 800 percent of that required for mole ratio 0 :P.,= 5. Ammoniainput ranged from 35 to 200 percent of that required for atomic ratio ofN:P 2. In some tests, N was added to the input gases as a diluent. Thetotal added N including carrier gas for phosphorus, was 65 weightpercent of the total charge of feed. In other tests, N was omitted as adiluent and used only as carrier gas for phosphorus. Air used in theprocess was dried to a dew point of F (0.000005 lb. water/lb. of dryair) by passing it through an anhydrous calcium sulfate absorptionsystem. The production rate, calculated on basis of recovery of allinput phosphorus as product (dry, white powders) containing 32 percentP, ranged from about 15 to 70 grams per hour to -235 grams per hour fortests in reactor tubes of 7 1.0- to 3.5-inch-inside diameter,respectively.

Prior investigators of the art of reacting phosphorus or phosphoruspcntoxide with ammonia or mixtures of ammonia and oxygen to preparenitrogen-phosphorus compositions of matter had to contend with theformation of some undesirable glassy materials, the presence of whichreduced the yield of reaction product. The glass was found to be aviscous, hygroscopic material that either adhered to the inner wall ofthe reaction vessel and/or collected with the product in receivingvessels such as bag filters or electrostatic precipitators.

In preliminary tests of our single-stage process, we, like those in theprior art referred to above, found that substantial proportions of thefeed deposited on the wall of the reactor as viscous, hygroscopic glass.The material was of about 7-85-0 grade. Tests made in a 2.5-inch-insidediameter reactor (mullite tube) indicated that glass formation on thewall of the reactor might be reduced somewhat by increasing the velocityof the gases through the reactor (1.7 vs. 0.5 ft./sec). This effect ofvelocity on glass formation was confirmed in tests with a smallerdiameter (1.0 in.) reactor; glass formation generally decreased withincrease in linear velocity (1.7-6.7 ft./sec.) and also with decrease inretention time (2.0-0.5 sec.). However, the proportions of glass werehigher in the tests with the smaller diameter reactor than with thelarger diameter reactor. These results indicated that reductions information of glass was favored by larger reactor diameter (lowersurfacezvolume ratio).

Referring now more specifically to FIG. 3, there is shown a curve ofrecovery of phosphorus as nonglass product (dry, white solids) versussurface area:volume ratio for tests that we made in various diametersinglestage reactors. This curve shows the very significant increases inproduct recovery that were effected by increasing reactor diameter(decreasing surface area:- volume ratio). A 3.5-inch-inside diameterreactor tube was the largest that we were able to use for conducting ourlaboratory tests of the scale smaller than that of a pilot plant orcommercial plant and of a size generally referred to as bench scale.Projection of the curve (broken line) indicates that phosphorus recoveryas product would approximate 100 percent if the reaction were carriedout in a cylindrical reactor tube of about -inch-inside diameter(surface area:volume ratio, 0.8). Recovery equipment of pilot-plantscale would be required however.

We obtained the best recovery of ammonia and phosphorus as usefulproduct, 80 and 95 percent, respectively, in our work with the 3.5-inchdiameter reactor (surface area:volume ratio, 1.14). The product was 75-0grade, 95 percent water soluble, and had good physical properties. Wehave found that the grade of the products and physical characteristicsfrom tests made in the 3.5-inch-diameter tube were about the same asthose obtained under similar conditions in tests with smaller diameterreactors.

In order that those skilled in the art may better understand how thepresent invention can be practiced and more fully and definitelyunderstood, the following examples of processes that we have used in thepreparation for the production of nitrogemphosphorus compounds preparedaccording to our invention are given by way of illustration and not byway of limitation.

EXAMPLE 1 The tubular single-stage reactor (FIG. 2) consisted of anelectrically heated tube of McDanel mullite (3.5-in [.D. by 24-in long).Phosphorus vapor (about 49.5 g/hr) with nitrogen carrier gas (1.3 g N /gP was fed from a calibrated saturator (about 374F) through a heatedglass line to the reactor maintained at 1000F.

Simultaneously, a gas mixture consisting of ammonia (1.1 volumepercent), dry air (34.2 volume percent equivalent to 7.2 volume percentoxygen) and nitrogen (N as a diluent (64.7 volume percent) were meteredto the reactor by means of glass laboratory flowmeters. The input gasmixtures (NI-I air N and P. N were heated to 500600F and broughttogether as they entered the reactor. The total added N includingcarrier for the phosphorus was 65 weight percent of the total charge offeed. The feed rate of ammonia, dry air, and nitrogen as a diluent were33, 1662, and 3038 grams per hour, respectively. Retention time of thegases in the reactor was 1.0 second at operating conditions. Linearvelocity of the input gases was 1.7 feet per second. The effectivereactor voluem was 3154 cubic centimeters. The total volume of gasescharged through the system was 63,715 cubic centimeters per minute(S.T.P.).

Oxygen (dry air) input was 600 percent of that required for a mole ratio0 5, and ammonia 60 percent of that required for atomic ratio N2? 2.

The gases leaving the reactor passed through a post reaction zone (1 in.ID. by about 10 in. long) where they were cooled to about 300F and thencollected in an electrostatic precipitator as dry, white powders.Unreacted ammonia was caught in a sulfuric acid scrubber.

The precipitator product was 15-7 50 grade and contained percent totalplant nutrient (N P 0 equivalent); percent of both nitrogen andphosphorus were water soluble at 77F. The N:P O weight ratio in theproduct was 0.20.

The recovery of ammonia and phosphorus as nonglass product (dry, whitepowders) in the precipitator was about 80 and 95 percent, respectively.If the N added (65 weight percent of the feed) was obtained by recyclingeffluent, ammonia utilization would be higher because some of theammonia would be recycled also. Input ammonia and phosphorus accountedfor as glass in the reactor was 2 and 5 percent, respectively. Theamount of ammonia as glass in the reactor was calculated by converting Precovered as glass in the reactor to grams of ammonia as glassy materialof grade 7-8- 5-0. About 13 percent of the input ammonia was recoveredin the acid scrubber and less than 5 percent was lost by cracking orotherwise was unaccounted for.

The results of other tests of the process with the single-stage reactorare shown in tables I through VI, infra.

EXAMPLE II Increasing the reactor diameter over the range of l .0 to 3.5inches decreased surface area:volume ratio from 4.00 to 1.14. This hadlittle, if any, effect on the products collected in the precipitators.The products were about the same grade (14-74-0 vs. 15-75-0) and hadabout the same water solubilities (92 vs. 95 percent of both N and P 0at 77F). All products had good physical properties (dry, white powders).

EXAMPLE 111 Increasing reactor diameter over the range of 1.0 to 3.5inches caused progressive increases in recovery of 10 ratio O :P 5.Total added N including carrier for phosphorus was 65 weight percent oftotal charge. Linear velocity was 1.7 feet per second. Retention time atoperating conditions was 1.0 second.

ammonia and phosphorus as non-glass product (dry, 5 EXAMPLE Iv whitepowders). Recovery of ammonia and phosphorus as product increased from27 to 65 and from 37 to 92 With 200 percent theoretical ammonia, theproduct percent, respectively. A recovery of input P approxiwas 1773-0grade and 58 percent water soluble. Demating 100 percent could beobtained if the reaction creasing theoretical ammonia from 200 percentto 80 were carried out in a reactor tube of about 5-inch inpercentcaused only aslight increase in grade (16-75-0 side diameter (FIG. 3,supra), i.e., a reactor surface vs. 17-73-0), but increased watersolubility of the areazvolume ratio of 0.8. For convenience, our testsproduct from 58 to 70 percent. Decreasing theoretical were carried outin tubular-type reactors since they ammonia from 80 to 70 percentincreased water soluwere easier to assemble and operate on our benchscale bility of the product from 70 to 92 percent. Product setup.However, it should be appreciated that perhaps grade was about the same(16-75-0 vs. 15-75-0). Deother shapes of reactor could conceivably proveto be creasing input ammonia from 70 percent to 60 percent as effectiveand might, on scaleup of our process, be incaused a further increase in'water solubility of the corporated in a full-size production plant. Inconsiderproduct (95 vs. 92 percent). Products obtained with ing this wehave reported the characteristics of our ammonia input from 200 percentto 60 percent of theoproduct not only in terms of diameter but also interms retical had good physical properties (dry, white powof reactorsurface area:volume ratio so that our readers ders). With a furtherdecrease in input ammonia to can make use of our data in scaling up withdifferent percent (test 188), the product was 13-77-0 grade, 98 shapereactors if they find it desirable. percent water soluble, but had poorphysical properties Table I Reaction of Ammonia, Phosphorus, and Oxygen(Air) Test No. 167A 177 181 183 Reactor tube l.D., in. Surfaceareazvolume ratio 4.00 2.00 1.33 1.14 Materials charged, g/hr (S.T.P.)

NH; 3.10 1.40 27.90 38.30 P, 4.00 15.00 36.70 48.90 Product (nong1ass)Composition Grade 15-75-0 15-74-0 14-74-0 15-75-0 W.S. N or P205 at 77F,of total 95 93 94 92 NzP Qr, weight ratio 0200 0.203 0.189 0.200Recovery, of charge Reactor temperature, [000F', ammonia input, ofamount required for atomic ratio NzP of2; oxygen (dry air) input, 600%ofamount required for mole ratio 0,:P, 5. Total added N, includingcarrier for phosphorus, 65 weight percent of total charge. Linearvelocity of input gases, 1.7 feet per second. Retention time, 1.0second. Collected in electrostatic precipitators as dry, white powders.

These data show (1) that reactor surface area:- volume ratio had littleeffect, if any, on composition and physical properties of the productsand (2) the very significant increases in recovery of ammonia andphosphorus as nonglass product that were affected by increasing reactordiameter (decreasing surface area:-

volume ratio). The temperature of the single-stage reactor was 1000F.The ammonia input was 70 percent of amount required for atomic ratio N:Pof 2. Oxygen (dry air) was 600 percent of amount required for mole(hygroscopic) due to its low N:P O weight ratio (0.169). A furtherdecrease in theoretical ammonia to 35 percent gave a material that wasvery wet and unsuitable for chemical analysis. The data show that theprocess must operate with proportions of input ammonia between about 60and 70 percent of theoretical to obtain the desired water solubility(about percent or greater of both N and P 0 contents of the products at77F).

"Reactor temperature, 1000F; oxygen (dry air) input, 600% of amountrequired for mole ratio 0,:1' 5.

Table Il-continued Reaction of Ammonia, Phosphorus, and Oxygen (Air)Product W.S. 72 of N or P N:P,O Condition on Test theoretical at 77F,weight removal from No. NH Grade 7: of total ratio precipitators Totaladded N, including carrier for phosphorus, 65 weight percent of totalcharge. Retention time, L0

second.

Percent theoretical ammonia based on amount required for atomic ratioN:P of 2,

EXAMPLE V With an oxygen (dry air) input of 800 percent of amountrequired for mole ratio 0 :1 5 and 1.0 second retention time, theproduct was 15-75-0 grade and 96 percent water soluble. Decreasingtheoretical oxygen (dry air) from 800 percent to 600 percent and thenfrom 600 percent to 375 percent resulted in products of about equalgrade (15-75-0 vs. 14-74-0) and about equal water solubility (96 vs. 94percent). All products were dry, white powders. Decreasing input oxygen(dry air) from 375 percent to 120 percent of theoretical changed theproduct from a dry, white powder to a sticky material which ignited onexposure to the atmosphere. With 120 percent input of oxygen (dry air),increasing the retention time from 1.0 to 3.5 seconds did not improvethe physical condition of the material.

oxygen (dry air) and N as diluent (65 weight percent of total charge),the product was 15-75-0 grade and 92 percent water soluble. Omitting Nas diluent decreased the grade from 15-75-0 to 14-74-0 and increased thewater solubility of the product from 92 to 98 percent. Both productswere dry, white powders.

EXAMPLE VII With lO0OF reactor temperature, percent theoretical inputammonia, 800 percent theoretical input oxygen (dry air) and N as diluentweight percent of total charge), the product was l5750 grade and 96percent water soluble. Omitting N as diluent decreased the grade from15-75-0 to 14-72-0 and increased water solubility of the product from 96to 100 percent. Both products were dry, white powders.

EXAMPLE VIII With l000F reactor temperature, 60 percent theoreticalinput ammonia, 375 percent theoretical input oxygen (dry air) and N as adiluent (65 weight percent of total charge), the product was l4740 gradeand 94 percent water soluble. Omitting N as diluent, de-

creased the grade from l474-0 to 14-71-0 and increased water solubilityof the product from 94 to 100 percent. Both products were dry, whitepowders.

Table III Reaction of Ammonia, Phosphorus, and Oxygen (Air) Product W.S.Reactor N or P 0 N:P,O Test theoretical retention N P 0 at 77F weightCondition on removal No. 2 2" time, sec. Grade equivalent of total ratiofrom precipitators 185 800 1.0 15-75-0 96 0.200 Dry, white powder 184600 1.0 l5-75-0 90 0.200 Dry, white powder 186 375 1.0 14-74-0 88 940.189 Dry, white powder 192 120 1.0 Sticky and ignited 194A 120 3.5Sticky and ignited "Ammonia input. 60 percent of amount required foratomic ratio N:P of 2. Total added N, including carrier gas forphosphorus, 65 weight percent of total charge.

Percent theoretical oxygen (dry air) based on amount required for moleratio 0,:P. S.

Temperature. l000F.

Collected in electrostatic precipitators.

EXAMPLE VI With l000F reactor temperature, 70 percent theoretical inputammonia, 600 percent theoretical input EXAMPLE IX With 800F reactortemperature, 60 percent theoretical input ammonia, 800 percenttheoretical input oxygen (dry air) and N as a diluent (65 weight percentof total charge), the product was 15-76-0 grade and 92 percent watersoluble. Omitting N as diluent decreased the grade from 15-76-0 to l5730and increased water solubility of the product from 92 to percent. Bothproducts were dry, white powders.

EXAMPLE X With 600F reactor temperature, 70 percent theoretical inputammonia, 600 percent theoretical input oxygen (dry air) and N as adiluent (65 weight percent of 13 total charge), the product was 15740and 92 percent water soluble. Omitting N as diluent, decreased the gradefrom 15-74-0 to 1470O and increased water 14 of 400F, increasingretention time from 1.0 to 3.5 seconds did not improve the physicalcondition of the material.

Table V Reaction of Ammonia, Phosphorus, and Oxygen (Air) Product" W.S.Reactor Reactor N or P N:P O Condition on temperature, retention N P 0at 77F. weight removal from Test No. F time, sec. Grade equivalent oftotal ratio precipitators 212 1350 1.0 Wet and sticky 206 1 150 1.0-74-0 89 92 0.203 Dry, white powder 186 1000 1.0 14-74-0 88 94 0.189Dry, white powder 191 800 1.0 15-76-0 91 93 0.197 Dry, white powder 190600 1.0 15-72-0 87 95 0.208 Dry, white powder 213 400 1.0 Wet 214 4003.5 Wet "Ammonia input. percent of amount required for atomic ratio N2?of 2. Oxygen (dry air) input, 375 percent of amount required for moleratio O :P,= 5. Total added N including carrier gas for phosphorus.weight percent of total charge. Collected in electrostaticprecipitatcrs.

solubility of the product from 92 to 100 percent. Both products weredry, white powders.

These data (Table V) show the effect of varying the temperature of thesingle-stage reactor on grade, water Table IV Reaction of Ammonia,Phosphorus, and Oxygen (Air) Product N,added as Reactor N or P 0 N:P,0

theoretical P charged, diluent, wt.% temp., N P 0 at 77F weight TestNo." N11 Ofg/hr (S.T.P.) of total charge F Grade equivalent of totalratio Reactor retention time, 1.0 second. N, as carrier for P 0.8-3.2g/g P Percent theoretical ammonia based on amount required for atomicratio NzP of 2.

Percent theoretical oxygen (dry air) based on amount required for moleratio 0,:P, 5.

Collected in electrostatic precipitators (dry. white powders). IncludesN, as carrier for P Does not include N, as carrier for P EXAMPLE XI Withreactor temperature of 1350F and 1.0 second retention time, a materialwas obtained in the precipitator that was wet and sticky. Decreasingreactor temperature to 1150F (test 206) gave a product of 15-74-0 grade,of 92 percent water solubility, and with good physical properties (dry,white powder). Further decreases in reactor temperature from 1150to1000F, from l000 to 800F, and from 800 to 600F resulted in products ofgrade l474-0, 15-76-0, and 15-72-0, respectively; water solubilities ofthe products were about the same (95 percent). These products were dry,white powders. Decreasing reactor temperature from 600 to 400F changedthe product from a dry, white powder to a wet material. With a reactortemperature solubility and physical properties of the products. Ammoniainput was 60 percent of amount required for atomic ratio N21 of 2.Oxygen (dry air) input was 375 percent of amount required for mole ratioO :P 5. Total added N including carrier for phosphorus was 65 weightpercent of total charge. Retention time at operating conditions was 1.0second except in test 214, where it was increased to 3.5 seconds.

EXAMPLE XII With reactor retention time of 3.5 seconds at operatingconditions, the product was 14-74-0 grade and 95 percent water soluble.Decreasing retention time from 3.5 to 1.0 second did not cause a changein grade and had little effect on the water solubility of the product(95 vs. 94 percent). Decreasing retention time to 0.5 second (test 169A)gave a product of lower grade (15-69-0 vs. l474-0), but did not affectthe water solubility significantly. All the products in thesev tests hadgood physical properties (dry, white powders). Decreasing retention timeto 0.1 second (test 215) caused formation of material which ignited onexposure to the atmosphere.

Table VI Reaction of Ammonia, Phosphorus, and Oxygen (Air) ProductReactor" N or P N:P O Condition on Test retention N P 0 at 77F, weightremoval from No. time, sec Grade equivalent of total ratio precipitators208 3.5 l4-74-0 88 95 0.189 Dry, white powder 186 1.0 l4-74-O 88 94 .189Dry, white powder l69A 0.5 -69-0 84 96 .217 Dry, white powder 215 0.1Ignited "Ammonia input, 60 percent of amount required for atomic ratioN:P of 2. Oxygen (dry air) input. 375 percent of amount required formole ratio O :P 5. Total added N including carrier gas for phosphorus.65 weight percent of total charge. Temperature, l000F. Collected inelectrostatic precipitators.

These data (Table VI) show the effect of reactor retention time ongrade, water solubility, and physical properties of the products.Reactor temperature was 1000F. Ammonia input was 60 percent of amountrequired for atomic ratio N:P of 2. Oxygen (dry air) input was 375percent of amount required for mole ratio O :P 5. Total added Nincluding carrier for phosphorus was 65 weight percent of total charge.

indicated that our product was a fully effective source of N and P.

After sifting and winnowing through the data presented above as well asother data available to us, we have determined that the operating limitsas well as the preferred and the most preferred conditions and variablesfor carrying out our process are as summarized below:

EXAMPLE XIII GREENHOUSE TEST Greenhouse tests of solid products (20-60percent water soluble at 77F) made by Lewis, Jr., from the re- 40 actionof NI-I -P -O (air) in the two-stage reactor, US Pat. No. 3,539,328supra, indicated that the products were available to crops to the extentof their water solubilities. Solutions of his products obtained byhydrolysis with steam under pressure were effective as sources ofnitrogen and phosphorus. Since our product made in the single-stagereactor was water soluble (about 90-100 percent), we believed it wouldbe effective as fertilizer.

A sample of our product was submitted for a shortterm greenhouse test.The product was made with the single-stage reactor operated at 1000F.Ammonia input was percent of amount required for atomic ratio N:P of 2.Oxygen (dry air) input was 375 percent of amount required for mole ratio0 2R, 5. Retention 55 time at operating conditions was 1.0 second.

The analysis of the product is tabulated below.

Reactor surface areazvolume ratio and N as a diluent are not listedsupra as reaction variables; they are, however, factors that we considerimportant for carrying out our process, particularly the reactor surfacearea: volume ratio. We have shown in Table I that recovery of ammoniaand phosphorus as nonglass product (dry, white powders) increasessignificantly with increases in reactor diameter (lower surfacezvolumeratio). Projection of the curve (broken line, FIG. 3) indicates that thesmallest reactor tube that could be used to carry out the reaction toobtain phosphorus recovery as product approximating percent would be oneof about S-inch-inside diameter, and having a maximum surfaceareazvolume ratio of about 0.8. The addition of nitrogen as a diluent tothe feed gases is optional, but omitting it (Table IV) decreases thegrade and increases the water solubility of the product.

While we have shown and described particular embodiments of ourinvention, modifications and variations thereof will occur to thoseskilled in the art. We wish it to be understood therefore that theappended The availability of the product was tested as sources ofN and Pfor corn in a conventional pot experiment in a 6-week growth period. Drymatter yields and uptakes claims are intended to cover suchmodifications and variations which are within the true scope and spiritof our invention.

What we claim as new and desire to secure by letters patent of theUnited States is:

1. A single-stage vapor phase reaction process involving ammonia,oxygen, and elemental phosphorus for the production of unusually highanalysis nitrogenphosphorus compositions eminently suitable for use asfertilizer material comprising the steps of:

l simultaneously introducing vapors of ammonia,

oxygen, and elemental phosphorus into a singlestage tubular reactionzone, said single-stage tubular reaction zone having a maximum surfacearea:- volume ratio of about 0.8 in /in;

2. maintaining in said single-stage tutular reaction zone a temperaturein the range of greater than about 400 and less than about 1350F2 3.controlling and proportioning the introduction of said vapors ofammonia, oxygen, and elemental phosphorus into said single-stage tubularreaction zone to maintain therein (a) an excess of oxygen in the rangefrom greater than about l percent up to about 800 percent (all percentsby weight) of that required to yield a O :P., mole ratio of 5, and (b) aquantity of ammonia in the range from greater than about 50 and lessthan about 80 percent of that required to yield a N:P atomic ratio of 4.maintaining the residence time of said vapors of ammonia, oxygen, andelemental phosphorus in said single-stage tubular reaction zone in therange from greater than about 0.1 second to less than about 4 seconds;and

18 5. withdrawing the resulting reaction product from said single-stagetubular reaction zone and collecting said product withdrawn from saidreaction zone as a substantially nonhygroscopic, amorphous, white,particulate solid nitrogen-phosphorus product having a predeterminedsolubility in water and containing a N:P O weight ratio in the rangefrom about 0.19 to about 0.23.

2. The process of claim 1 wherein the temperature in said reaction zoneis maintained in the range of about 500 to about 1300F.

3. The process of claim 2 wherein the amount of excess oxygen in step(3) thereof ranges from about 375 to about 600 percent.

4. The process of claim 3 wherein the amount of ammonia in step (3)thereof ranges from about 60 to percent. I

5. The process of claim 4 wherein the residence time in step (4) thereofis in the range of about 0.5 to about 3.5 seconds.

6. The process of claim 5 wherein the temperature in the reaction zoneis maintained in the range of about 600 to about 1150F.

7. The process of claim 6 wherein the amount of excess oxygen in step(3) thereof is maintained at about 375 percent.

8. The process of claim 7 wherein the amount of ammonia in step (3thereof is maintained at about 60 percent of thatrequired.

9. The process of claim 8 wherein the reaction time in step (4) thereofis maintained at about 1 second.

1. A SINGLE-STAGE VAPOR PHASE REACTION PROCESS INVOLVING AMMONIA,OXYGEN, AND ELEMENTAL PHOSPHORUS FOR THE PRODUCTION OF UNUSUALLY HIGHANALYSIS NITROGEN-PHOSPHORUS COMPOSITIONS EMINENTLY SUITABLE FOR USE ASFERTILIZER MATERIAL COMPRISING THE STEPS OF:
 1. SIMULTANEOUSLYINTRODUCING VAPORS OF AMMONIA, OXYGEN, AND ELEMENTAL PHOSPHORUS INTO ASINGLE-STAGE TUBULAR REACTION ZONE, SAID SINGLE-STAGE TUBULAR REACTIONZONE HAVING A MAXIMUM SURFACE AREA:VOLUME RATIO OF ABOUT 0.8 IN2/IN3; 2.MAINTAINING IN SAID SINGLE-STAGE TUTULAR REACTION ZONE A TEMPERATURE INTHE RANGE OF GREATER THAN 400* AND LESS THAN ABOUT 1350*F: 2.maintaining in said single-stage tutular reaction zone a temperature inthe range of greater than about 400* and less than about 1350*F:
 2. Theprocess of claim 1 wherein the temperature in said reaction zone ismaintained in the range of about 500* to about 1300*F.
 3. controllingand proportioning the introduction of said vapors of ammonia, oxygen,and elemental phosphorus into said single-stage tubular reaction zone tomaintain therein (a) an excess of oxygen in the range from greater thanabout 120 percent up to about 800 percent (all percents by weight) ofthat required to yield a O2:P4 mole ratio of 5, and (b) a quantity ofammonia in the range from greater than about 50 and less than about 80percent of that required to yield a N:P atomic ratio of 2;
 3. Theprocess of claim 2 wherein the amount of excess oxygen in step (3)thereof ranges from about 375 to about 600 percent.
 3. CONTROLLING ANDPROPORTIONING THE INTRODUCTION OF SAID VAPORS OF AMMONIA, OXYGEN, ANDELEMENTAL PHOSPHORUS INTO SAID SINGLE-STAGE TUBULAR REACTION ZONE TOMAINTAIN THEREIN (A) AN EXCESS OF OXYGEN IN THE RANGE FROM GREATER THANABOUT 120 PERCENT UP TO ABOUT 800 PERCENT (ALL PERCENTS BY WEIGHT) OFTHAT REQUIRED TO YIELD A O2:P4 MOLE RATIO OF 5, AND (B) A QUANTITY OFAMMONIA IN THE RANGE FROM GREATER THAN ABOUT 50 AND LESS THAN ABOUT 80PERCENT OF THAT REQUIRED TO YIELD A N:P ATOMIC RATIO OF 2; 4.MAINTAINING THE RESIDENCE TIME OF SAID VAPORS OF AMMONIA, OXYGEN, ANDELEMENTAL PHOSPHORUS IN SAID SINGLESTAGE TUBULAR REACTION ZONE IN THERANGE FROM GREATER THAN ABOUT 0.1 SECOND TO LESS THAN ABOUT 4 SECONDS;AND
 4. The process of claim 3 wherein the amount of ammonia in step (3)thereof ranges from about 60 to 70 percent.
 4. maintaining the residencetime of said vapors of ammonia, oxygen, and elemental phosphorus in saidsingle-stage tubular reaction zone in the range from greater than about0.1 second to less than about 4 seconds; and
 5. withdrawing theresulting reaction product from said single-stage tubular reaction zoneand collecting said product withdrawn from said reaction zone as asubstantially nonhygroscopic, amorphous, white, particulate solidnitrogen-phosphorus product having a predetermined solubility in waterand containing a N:P2O5 weight ratio in the range from about 0.19 toabout 0.23.
 5. The process of claim 4 wherein the residence time in step(4) thereof is in the range of about 0.5 to about 3.5 seconds. 5.WITHDRAWING THE RESULTING REACTION PRODUCT FROM SAID SINGLE-STAGETUBULAR REACTION ZONE COLLECTING SAID PRODUCT WITHDRAWN FROM SAIDREACTION ZONE AS A SUBSTANTIALLY NONHYGROSCOPIC, AMORPHOUS, WHITE,PARTICULATE SOLID NITROGEN-PHOSPHORUS PRODUCT HAVING A PREDETERMINEEDSOLUBILITY IN WATER AND CONTAINING A N:P2O5 WEIGHT RATIO IN THE RANGEFROM ABOUT 0.19 TO ABOUT 0.23.
 6. The process of claim 5 wherein thetemperature in the reaction zone is maintained in the range of about600* to about 1150*F.
 7. The process of claim 6 wherein the amount ofexcess oxygen in step (3) thereof is maintained at about 375 percent. 8.The process of claim 7 wherein the amount of ammonia in step (3 )thereof is maintained at about 60 percent of that required.
 9. Theprocess of claim 8 wherein the reaction time in step (4) thereof ismaintained at about 1 second.